DNA REPLICATION PYQ Archives - Page 5 of 9 - CSIR NET LIFE SCIENCE COACHING | NTA NET LIFE SCIENCE

Slug: ecoli-dna-polymerase-i-iii-processivity-exonuclease Title: Understanding E. coli DNA Polymerase I and III: Processivity, Exonuclease Activities, and Roles in Replication Meta Description: Explore the distinct roles of DNA polymerase I and III in Escherichia coli replication, focusing on processivity, exonuclease activities, and suitability for leading and lagging strand synthesis. Analysis of Each Statement (A) DNA Pol I displays very limited processivity and possesses 3′→5′ exonuclease activity, allowing fidelity of DNA replication. True: DNA polymerase I has limited processivity compared to Pol III and possesses 3′→5′ exonuclease proofreading activity that enhances fidelity during DNA synthesis. However, its processivity is low, making it unsuitable for bulk replication. (B) DNA Pol III is suitable for leading strand DNA synthesis due to its high processivity and 5′→3′ exonuclease activity that removes incorrect nucleotides incorporated during DNA synthesis. Partially incorrect: DNA polymerase III is highly processive and suitable for leading strand synthesis. However, the proofreading exonuclease activity is 3′→5′, not 5′→3′. The 5′→3′ exonuclease activity is characteristic of Pol I, not Pol III. Pol III lacks 5′→3′ exonuclease activity. (C) DNA Pol I possesses 5′→3′ exonuclease activity which allows removal of the RNA primer while its 3′ polymerase activity allows it to fill the gap created by removal of the RNA primer. True: DNA polymerase I uniquely has 5′→3′ exonuclease activity to remove RNA primers and 5′→3′ polymerase activity to fill in the gaps with DNA. (D) DNA Pol III is suitable for lagging strand DNA synthesis due to its low processivity and 5′→3′ exonuclease activity. False: DNA polymerase III has high processivity, essential for lagging strand synthesis. It also lacks 5′→3′ exonuclease activity; this activity is present in Pol I. Summary Table Statement Correctness Explanation A Correct Pol I has limited processivity and 3′→5′ exonuclease proofreading activity. B Incorrect Pol III is highly processive but does not have 5′→3′ exonuclease activity; proofreading is 3′→5′. C Correct Pol I removes RNA primers via 5′→3′ exonuclease and fills gaps with polymerase activity. D Incorrect Pol III has high processivity and lacks 5′→3′ exonuclease activity. Correct Combination of Statements (4) A and C Explanation DNA polymerase I is specialized for primer removal and gap filling with limited processivity but has proofreading ability. DNA polymerase III is the main replicative polymerase with high processivity and 3′→5′ exonuclease proofreading activity but lacks 5′→3′ exonuclease activity. The 5′→3′ exonuclease activity for primer removal is unique to DNA polymerase I. Keywords E. coli DNA polymerase I, DNA polymerase III, processivity, exonuclease activity, 3′→5′ proofreading, 5′→3′ exonuclease, leading strand synthesis, lagging strand synthesis, RNA primer removal, Okazaki fragments Final Answer: (4) A and C

CSIR NET Life Science Previous Year Questions and Solution on DNA REPLICATION

Understanding E. coli DNA Polymerase I and III: Processivity, Exonuclease Activities, and Roles in Replication

admin
June 14, 2025
21 Comments

The following statements refer to the E. coli replicative DNA polymerase: (A) DNA POI I displays very limited processivity and possesses 3’à5′ exonuclease activity, allowing fidelity of DNA replication. (B) […]

47. for Escherichia coli chromosomal DNA replication, which one of the following statements is true? (1) DNA polymerase I is the main polymerase required for DNA replication (2) DNA polymerase I though identified originally by Kornberg as the one responsible for replication, is not important for the DNA replication process (3) Requirement of DNA polymerase I is in the context of removal of RNA primer needed for DNA synthesis, and then fill in the same with DNA equivalent (4) DNA polymerase I is the primary enzyme for error prone DNA synthesis in response to SOS.

CSIR NET Life Science Previous Year Questions and Solution on DNA REPLICATION

Understanding the Role of DNA Polymerases in E. coli Chromosomal DNA Replication

admin
June 14, 2025
25 Comments

for Escherichia coli chromosomal DNA replication, which one of the following statements is true? (1) DNA polymerase I is the main polymerase required for DNA replication (2) DNA polymerase I […]

46. Nick translation means (1) Translation by cytosolic ribosome (2) Translation of protein from stalled sites (3) Replication by ONA polymerase I after removing RNA primers (4) Replication of DNA by DNA polymerase I from nicks produced by DNase treatment

CSIR NET Life Science Previous Year Questions and Solution on DNA REPLICATION

What is Nick Translation? Mechanism and Role of DNA Polymerase I in DNA Labeling and Repair

admin
June 14, 2025
29 Comments

Nick translation means (1) Translation by cytosolic ribosome (2) Translation of protein from stalled sites (3) Replication by ONA polymerase I after removing RNA primers (4) Replication of DNA by […]

45. Which of the following statement is correct with reference to replication in eukaryotes? (1) Single origin and continuous replication (2) Multiple origin and semi-discontinuous replication (3) Multiple origin and continuous replication (4) Single origin and semi-discontinuous replication

CSIR NET Life Science Previous Year Questions and Solution on DNA REPLICATION

Understanding Eukaryotic DNA Replication: Multiple Origins and Semi-Discontinuous Synthesis Explained

admin
June 14, 2025
30 Comments

Which of the following statement is correct with reference to replication in eukaryotes? (1) Single origin and continuous replication (2) Multiple origin and semi-discontinuous replication (3) Multiple origin and continuous […]

44. Among the following which DNA polymerase lacks proof reading activity? (1) DNA polymerase α primase activity (2) DNA polymerase Ꟙ (3) DNA polymerase ϵ (4) Both DNA polymerase α and ϵ

CSIR NET Life Science Previous Year Questions and Solution on DNA REPLICATION

Which DNA Polymerases Lack Proofreading Activity? Understanding 3′→5′ Exonuclease Functions in DNA Replication

admin
June 14, 2025
30 Comments

Among the following which DNA polymerase lacks proof reading activity? (1) DNA polymerase α primase activity (2) DNA polymerase Ꟙ (3) DNA polymerase ϵ (4) Both DNA polymerase α and […]

43. DNA repair, synthesis and recombination are intimately connected and inter dependent. An apparent commonality between processes of DNA replication and repair in the enzymatically catalyzed synthesis of DNA polynucleotide segments, which can be assembled with pre-existing polynucleotides, leading to repair or replication. Synthesis of these polynucleotide segments is catalyzed by a group of enzymes DNA-dependantDNA polymerases. In the case of E.coli, DNA polymerase has been isolated in three distinct forms whereas five main types of polymerase have been isolated from mammalian cells. All the polymerases synthesize polynucleotides only in the 5'3' direction. If polynucleotide chains could be elongated in 3’5' direction, the hypothetical growing 5' terminus, rather than the incoming nucleotide, would carry a tri- phosphate that is unsuitable for further elongation. The 3'5' exonuclease activity is not associated with all the polymerases and only present in (A) All E. coli DNA polymerases (B) Pol l, Pol IV, Pol V, Pol α, Polβ. (C) Pol l, Pol III, Poi Ꟙ, Poi ϵ (D) Pol l, Pol IV, POlα, Poi ϵ. The correct statements are (1) (A) and (B) (2) (A), (B) and (C) (3) (C) only (4) (A), (C) and (D)

CSIR NET Life Science Previous Year Questions and Solution on DNA REPLICATION

Which DNA Polymerases Possess 3′→5′ Exonuclease (Proofreading) Activity in E. coli and Mammals?

admin
June 14, 2025
17 Comments

DNA repair, synthesis and recombination are intimately connected and inter dependent. An apparent commonality between processes of DNA replication and repair in the enzymatically catalyzed synthesis of DNA polynucleotide segments, […]

42, During replication, the RNA primer is degraded by the 5' - 3' exonuclease activity of (1) RNAseH (2) FEN-1 (flap endonuclease 1) (3) Topoisomerase II B (4) DNA polymerase

CSIR NET Life Science Previous Year Questions and Solution on DNA REPLICATION

Which Enzyme Removes RNA Primers During DNA Replication Using 5′→3′ Exonuclease Activity?

admin
June 14, 2025
37 Comments

42, During replication, the RNA primer is degraded by the 5′ – 3′ exonuclease activity of (1) RNAseH (2) FEN-1 (flap endonuclease 1) (3) Topoisomerase II B (4) DNA polymerase […]

41. In the diagram below, the dotted line marks the point of initiation of bidirectional replication c, A. On the right side of the dotted line, leading strand synthesis occurs using the upper strand as the template. B. On the right side of the dotted line, leading strand synthesis occurs using the lower strand as the template. C. A ligase deficient (lig-) mutant would affect replication of the upper strand on the left side of the dotted line. D. A ligase deficient (lig-) mutant would affect replication of the lower strand on the left side of the dotted line. Which one of the following options represents the combinations of the correct statements? (1) A and D (2) B and C (3) B and D (4) A and C

CSIR NET Life Science Previous Year Questions and Solution on DNA REPLICATION

Understanding Leading Strand Synthesis and Ligase Deficiency Effects in Bidirectional DNA Replication

admin
June 14, 2025
15 Comments

41. In the diagram below, the dotted line marks the point of initiation of bidirectional replication c, A. On the right side of the dotted line, leading strand synthesis occurs […]

40. The long DNA strand depicted below is serving as a template for lagging strand DNA synthesis. The short lines represent the newly synthesized okazaki fragments. At which position among A, B, C and D would DNA primase act next? (1) A (2) B (3) C (4) D

CSIR NET Life Science Previous Year Questions and Solution on DNA REPLICATION

Determining the Next Site of DNA Primase Action in Lagging Strand DNA Synthesis

admin
June 14, 2025
22 Comments

40. The long DNA strand depicted below is serving as a template for lagging strand DNA synthesis. The short lines represent the newly synthesized okazaki fragments. At which position among […]

39. In the figure above, replication of DNA beginning from the origin of replication of the chromosome of a newly identified bacterium having a double stranded circular DNA genome is shown. Characterization of DNA polymerase responsible for genome replication showedthat DNA synthesis occurred in to direction and it depends on the presence of a primer (as is the case in Escherichia coli). Polarities ot DNA (5' or 3') are as shown. Replication begjns at a point marked ‘O’ on the left of the bubble. and both the parent strands were replicated concurrently. The longer arrow inside the bubble shows the leading strand, whereas the shorter arrows (marked a, b, c) show the Okazaki fragments. The model depicts a: (i) bidirectional mode of replication wherein synthesis of the Okazaki fragment marked 'c' occurs prior to those marked 'a' and 'b' (2) bidirectional mode of replication wherein synthesis of the Okazaki fragment marked 'a' occurs prior to those marked 'b' and 'c' (3) unidirectional mode of replication wherein synthesis of the Okazaki fragment marked 'c' occurs prior to those marked 'a' and 'b'. (4) unidirectional mode of replication wherein synthesis of the Okazaki fragment marked 'a' occurs prior to those marked 'b' and 'c'.

CSIR NET Life Science Previous Year Questions and Solution on DNA REPLICATION

Bidirectional Replication and Okazaki Fragment Synthesis Order in Circular Bacterial Chromosomes

admin
June 14, 2025
20 Comments

In the figure above, replication of DNA beginning from the origin of replication of the chromosome of a newly identified bacterium having a double stranded circular DNA genome is shown. […]

Tag: DNA REPLICATION PYQ

Understanding E. coli DNA Polymerase I and III: Processivity, Exonuclease Activities, and Roles in Replication

Understanding the Role of DNA Polymerases in E. coli Chromosomal DNA Replication

What is Nick Translation? Mechanism and Role of DNA Polymerase I in DNA Labeling and Repair

Understanding Eukaryotic DNA Replication: Multiple Origins and Semi-Discontinuous Synthesis Explained

Which DNA Polymerases Lack Proofreading Activity? Understanding 3′→5′ Exonuclease Functions in DNA Replication

Which DNA Polymerases Possess 3′→5′ Exonuclease (Proofreading) Activity in E. coli and Mammals?

Which Enzyme Removes RNA Primers During DNA Replication Using 5′→3′ Exonuclease Activity?

Understanding Leading Strand Synthesis and Ligase Deficiency Effects in Bidirectional DNA Replication

Determining the Next Site of DNA Primase Action in Lagging Strand DNA Synthesis

Bidirectional Replication and Okazaki Fragment Synthesis Order in Circular Bacterial Chromosomes

Latest Courses

IIT JAM / CUET- PG

CSIR UGC NET Life Science Course

ICMR JRF Life Science